In ASP.NET, the statement “Cache events are processed whenever a postback event occurs” is being evaluated. Is this statement correct or incorrect?

Introduction / Context:
ASP.NET provides built in caching mechanisms to store data in memory and improve performance. It also has a life cycle model with postback events for Web Forms pages. Although both concepts affect how applications behave, cache events and postback events serve very different purposes. Interviewers sometimes ask questions like this to see if you can separate caching concepts from page event handling.

Given Data / Assumptions:

• We are using ASP.NET Web Forms or an environment with output or data caching.
• Postbacks occur when a page submits data back to itself on the server.
• Cache entries may have expiration policies or callbacks.
• The statement claims that cache events are processed whenever postback events occur.

Concept / Approach:
ASP.NET caching and postback events are independent features. Postback events relate to the page life cycle and user interactions with server controls. Cache events, such as removal callbacks, are triggered when cache entries expire, are removed, or dependencies change. A postback may read from or write to the cache, but it does not automatically cause cache events to fire. Therefore, the statement that cache events are processed whenever postback events occur is not accurate.

Step-by-Step Solution:
Step 1: In a Web Forms application, a postback happens when a form is submitted back to the same page URL, and ASP.NET processes page events such as Button.Click. Step 2: Cache entries in ASP.NET can be configured with absolute or sliding expiration, dependencies such as files, or change monitors. Step 3: When the expiration time is reached or a dependency changes, the cache removes the entry and can invoke a callback method to notify the application. Step 4: These cache callbacks occur independently of postback events; they are based on time or dependency changes, not simply on the occurrence of a postback. Step 5: A postback might happen without any cache entry expiring, and cache entries might expire between requests, confirming that the two processes are separate.

Verification / Alternative check:
You can validate this by creating a cache item with a short expiration and a removal callback, then watching logs while making multiple postbacks. Some postbacks will occur without triggering the cache callback if the item has not yet expired, and the callback may trigger between user actions due to time based expiration. This behaviour clearly shows that cache events are not tied directly to postback events.

Why Other Options Are Wrong:
Option B is wrong because it claims every postback always triggers cache events, which is not supported by how the caching API works. Option C is incorrect because cache events and postback events are distinct concepts, not the same mechanism. Option D is wrong because ASP.NET Web Forms clearly supports postback events; they are central to its operation.

Common Pitfalls:
A common pitfall is assuming that data in cache will be refreshed automatically on each postback, leading to stale data if expiration rules are not configured correctly. Another issue is forgetting that callbacks may run outside of direct user actions, so code inside them must be thread safe and not assume the existence of a current request context. Separating the concerns of caching and page events helps you design more predictable and scalable ASP.NET applications.

Final Answer:
The statement is incorrect, because cache related events occur when cache entries expire or are invalidated based on their policies, not automatically whenever a postback event occurs.